1. Technical Field
The present invention is directed to an apparatus and a method for digital image processing and more particularly to an apparatus and a method for minimizing the visual perception of artifacts associated with contouring.
2. Description of the Prior Art
When processing digital images it is often necessary to use quantizers to express the processed image data in a digital format. When quantizing is applied it may create a contouring problem. Contouring is the creation of a visual effect that was not present in the original image before it was digitally processed. Digital image processing systems which process signals that are gamma corrected, filtered, convoluted, spatially operated upon, color space converted and/or interpolated have a particular need for solving the contouring problem. This need arises due to the fact that the previously-mentioned processes introduces a gain that causes an image data to have a value that is greater than what the system can handle. Such being the case, these gains will in turn introduce missing codes. If the missing codes occur in a non-random manner, such that they repeat for a large number of times, they will be visible to the human eye when an image is formed using signals that have these codes missing. With large gains, any quantization steps that are used also becomes large and therefor more noticeable when images are formed using these quantized results. The missing codes can be manipulated to reduce this contouring problem by causing their existence to occur in a random pattern within the systems maximum computational gain value. With a random pattern the human eye has more difficulty in noticing the pattern. If the pattern is random enough the eye will miss it altogether.
The present apparatus and method are directed to a solution for minimizing the contouring problem.